PR enclosure question

Discussion in 'Archived Threads 2001-2004' started by ChristopherW, Jan 7, 2003.

  1. ChristopherW

    ChristopherW Agent

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    This is a question to all you PR enclosure experts, or anyone who whats to chime in.

    I was wondering if there is a preferred configuration for the drivers and PR's. In my enclosure I will have 1 AV12 and 2 15" PR's. Is it OK to have the driver firing downward with the PR's on the vertical sides? Or is it better to have the driver front firing and the PR's still on the vertical sides?

    The holes on my box are already cut, so for me its a matter of the foot print size of the sub. I would prefer a smaller footprint, but it would require the driver to be down firing.

    Thanks for the advice in advance.
     
  2. Jack Gilvey

    Jack Gilvey Producer

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  3. Craig Woodhall

    Craig Woodhall Supporting Actor

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    I was told by a guy that builds boxes (and my box too) professionally that you don't want the driver down-firing but on the same plane as the PR's.. So with my tumult enclosure, I am putting the driver on one side (vertically) and the 2 PR's on opposing sides..

    Craig
     
  4. ChristopherW

    ChristopherW Agent

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    Thanks for the input guys.

    Craig,
    Is there a reason they should be on the same plane?
     
  5. Craig Woodhall

    Craig Woodhall Supporting Actor

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    Chris,

    Jack knows more than me, im just going by what the professional speaker builder told me when I was gonna put my Tumult down firing.. Maybe someone else has another opinion..

    Craig
     
  6. ChristopherW

    ChristopherW Agent

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    Thanks Craig

    Jack,

    I know you have alot of experience with PR enclosures. So in you opinion driver placement, whether foward or down firing shouldn't matter as long as it doesn't adversely effect the driver (AV12), correct? The most important thing is to have the PR's vertically mounted on opposing sides, right? Would you happen to know if it is ok to mount a Stryke AV12 in a downfiring position?
     
  7. Greg Monfort

    Greg Monfort Supporting Actor

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    Hmm, rotate your sub so the driver is at the bottom and it's still on the same plane as the PRs, only the vertical, instead of the horizontal one.
    Even if it wasn't on the same plane, the driver pressurizes the cab, with its excursion falling in time with the increase of the PR's excursion until it ~stalls out at Fb and the PRs are doing all the excursing, so what flippin' difference does it make? [​IMG] I mean, keeping drivers on the same vertical plane is good engineering for higher/smaller, more directional frequencies, but WLs >11ft? Gimme a break! [​IMG]
    Really, the only issue I can think of is coupled rocking motions. Ideally you want two opposed drivers to go with two or four opposed PRs to ~cancel them all out, so with only a single driver there will be out of BW vibration that will need to be damped down through mass loading, but I don't see how the driver to PR orientation could add any additional vibrations or increased energy of the same ones of any consequence in a typical sub design.
    I hope this 'pro' knows a lot more about sub box construction than he appears to about driver orientation WRT PRs. I'm interested in hearing his thoughts on this though, just in case I'm not 'seeing the forest for the trees' since I've never done a single driver/dual PR sub, only dual/dual.
    GM
     
  8. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    When I hear "Driver on the same plane as the PR's" I'm thinking that means the driver is on the same panel as one of the PR's. But others apparently think that having the driver on the front panel and a PR on each of the right and left sides counts as "on the same plane".

    Craig's 2nd post sounds like this, though its not completely clear:
    "I am putting the driver on one side (vertically) and the 2 PR's on opposing sides"

    Greg's post above sounds like this:
    "rotate your sub so the driver is at the bottom and it's still on the same plane as the PRs, only the vertical, instead of the horizontal one."

    But I'm thinking if the driver is at a 90 degree angle to the PR's its not the same plane. It can be 180 degrees or 0 degrees, but nothing else. The 'pro' could be concerned that vibrations from the driver, might affect the alignment of the PR's as they travel through their excursion.

    If you've got an even number of drivers and PR's then I don't think it matters since you could place drivers opposite each other and PR's opposite each other and everything's balanced.
     
  9. Craig Woodhall

    Craig Woodhall Supporting Actor

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    He is building boxes for a bunch of stuff with Adire audio and other things at the CES show so I have lots of confidence in him.. I will ask the reasoning when I talk to him later.. If my last post was unclear, I will have my Tumult forward facing and then the 2 18" PR's on 2 of the sides, opposing each other..

    Craig
     
  10. Greg Monfort

    Greg Monfort Supporting Actor

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    >When I hear "Driver on the same plane as the PR's" I'm thinking that means the driver is on the same panel as one of the PR's.
    ====
    His alleged statement implies both PRs. I think we can all agree that this isn't a good plan unless it's made from re-inforced concrete, or at least has a couple of sand bags stacked on top to mass load them. [​IMG]
    ====
    > But others apparently think that having the driver on the front panel and a PR on each of the right and left sides counts as "on the same plane".
    >But I'm thinking if the driver is at a 90 degree angle to the PR's its not the same plane. It can be 180 degrees or 0 degrees, but nothing else. The 'pro' could be concerned that vibrations from the driver, might affect the alignment of the PR's as they travel through their excursion.
    ====
    Well, IIRC 42yr old plane geometry, if a line intersects two or more points then they're on the same plane, so whether they're all on the same panel or on the same line of a three dimensional object they're all on the same plane, and this plane can be rotated up to 360deg.
    Regardless, until I hear a compelling argument to the contrary, it's BS to me, probably well intentioned BS, but still BS.
    GM
     
  11. Dan Wesnor

    Dan Wesnor Second Unit

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    The PR's will have a lot of mass and move a lot. Place them on opposite sides of the box so they'll mechanically null each other out. As somebody said, if you don't do this, it'll dance across the floor.

    Any arguments about using the PR's motion to cancel out the driver's motion are bunk, since the drivers and the PR will not be moving together (when the PR's have the most motion, the driver should actually stand still).

    Even though it may be OK to have a subwoofer downfiring, I still recommend you don't do this. At the very least, you'll eat up some Xmax (reducing total output), and at worst, the driver may sag in a few years from the constant force in one direction only.
     
  12. ChristopherW

    ChristopherW Agent

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    Dan,

    Thanks for the info. With regards to the downward firing position could you tell me how much it will effect the output of the sub. Over the long haul will the effects be noticeable? Will the driver eventually "wear out"?
     
  13. Craig Woodhall

    Craig Woodhall Supporting Actor

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    I always said put the PR's opposing each other in case that point wasn't made..

    Craig
     
  14. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    Greg,

    I think the geometric terminology was used loosely (innacurately) and caused the confusion. I'm sure nobody meant to imply that both PR's should be mounted in the same panel. We all agree that they should be opposite each other. Perhaps the wording should have been something more like

    "The driver should be mounted on a plane that is parallel to the PR"s"

    Lets say, for example, the PR's are mounted on the front and back panels so that their excursion is forwards/backwards. Where do we mount the driver? If we mount it on the top or bottom then there will be some unbalanced motion as the driver moves up/down. This up/down motion may affect the alignment of the PR's since they're only intended to move forwards/backwards. If we mount the driver on the right side or left side then there will be some unbalanced motion as the driver moves left/right. Again, this could affect the alignment of the PR's which want to move only forwards/backwards. If the driver is mounted on the front or back then the unbalanced motion will be forwards/backwards. It will always add to one of the PR's excursion and subtract from the other. But it won't mess with the alignment of the PRs. Of course the driver would have to be off-axis with the PR's so there'd still be some undesirable effect, but to a lesser degree than the 2 previous cases.

    I'm not really trying to support this argument but rather just explain what I think this "professional" was trying to say. You said you were interested in hearing thoughts on this and to me this seemed like something to at least consider.
     

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